To extend the target range for development of anti-retroviral agents, we are focusing on HIV-1 integrase inhibitors using recombinant enzyme and short oligonucleotides corresponding to the proviral ends (LTR's). Integrase is a rationale target for drug development because it is essential for viral replication. It is encoded by HIV and does not have a cellular equivalent. Our laboratory has pioneered the integrase inhibitors research field, discovered several families of lead inhibitors and patented some with the aim of therapeutic development. Recently, the first class of selective HIV-1 integrase inhibitors with demonstrated antiviral activity related to integrase inhibition has been introduced in clinical trials. We are investigating these diketo acid (DKA) derivatives in collaboration with Dr. Terrence Burke (Laboratory of Medicinal Chemistry, CCR, NCI) and Dr. Vinay Pathak (Antiviral Drug Resistance Program, CCR, NCI). Our goals are to elucidate the molecular pharmacology of the DKA, and more specifically their binding site in the integrase-DNA complex. We are performing structure-activity relationship and collaborating with David Davies' crystallography group (NIDDK). We found that azido derivatives of diketo acids are potent and selective anti-integrase inhibitors and are antiviral. A patent application has been filed for our derivatives. We recently found in collaboration with Dr. Peter Roller (Laboratory of Medicinal Chemistry, CCR, NCI) that cationic peptides derived from indolicidin are integrase inhibitors. Their mechanism of action is novel as they bind to DNA, and thereby interfere with the formation of competent integrase-DNA complexes. In parallel, we are studying the molecular interactions between integrase and its DNA substrate using site-directed mutagenesis and enzyme-DNA crosslinking assays.